unknown table saw (?) accessory

by Ray Elkins
(Murray, KY)

I have quite a collection and very rarely do I come across something I can't identify, but this one has me stumped. I inherited a shop full of great old tools from my grandfather who retired from a career as a patter-maker and machinist. This accessory was in his stuff. It fits standard miter slots in my table saws, router tables, oscillating spindle sander, and belt/disc sander. The long arm has a sharp pin on the bottom. What this thing does, I am dying to know!